1. Field of the Invention
This invention relates to a circuit for use in a factory automation apparatus, for example, a programmable controller, a numerical control apparatus, a robot controller, or the like.
More specifically, this invention relates to an output module of a factory automation apparatus, which is used as an electronic switch.
2. Description of the Related Art
Output modules are used for turning ON/OFF of loads in numerical control apparatus, program controllers and robot controllers.
The loads, which are the object of control, are operated with many kinds of power sources, such as AC 100 V, AC 200 V, DC 24 V, DC 100 V or the like. Therefore, in the related art, special output circuits are prepared for these power sources, which are suitable to the object of control. These special output circuits are called, for example, an output module for AC 100 V, an output module for DC 24 V or another descriptive name which explains the voltage for which it is intended.
Output modules of the related art are shown in FIG. 7 and FIG. 8.
In FIG. 7, output signal ON is input to light emitting diode 200a of optoisolator photo coupler 200 though inverter driver 100. The collector of photo-transistor 200b is connected to resistor 300 and the emitter of photo-transistor 200b is connected to resistor 400. Other terminals of these resistors are connected to output terminal OT 1 and output terminal OT 3 respectively. The other terminal of resistor 400 is connected to the base of transistor 500 and the output terminal OT 3 side of resistor 400 is also connected to emitter of transistor 500. The collector of transistor 500 is connected to output terminal OT 2. The positive pole of DC power supply DPS is connected to output terminal OT 1 and also connected to output terminal OT 2 via load LD. Further the negative pole of DPS is connected to output terminal OT 3.
In this organization of the related art, photo diode 200a emits light in response to the ON/OFF state of output signal ON which is input to inverter driver 100, and then photo-transistor 200b also turns ON/OFF. Accordingly base emitter voltage of transistor 500 is supplied in accordance with the divided voltage ratio between resistor 300 and resistor 400 and then transistor 500 turns ON/OFF. This provides a current path so that the power supply to load LD is achieved.
FIG. 8 shows the ON/OFF signal of output signal ON applied to inverter driver 100 and passes through photo-triac 600, to cause triac 700 to turn ON/OFF. Further load LD which is connected between anode and cathode of triac 700, which is for instance, a solenoid or the like, is driven by alternating current power source APS.
As mentioned above, it is conventional to prepare a semiconductor triac for an AC load and to use a transistor for DC load.
However, a triac generally can not turn ON/OFF a DC load. Also when a transistor is used for switching a DC load, an N channel transistor or an P channel transistor must be used properly based on the polarity of a load.
Therefore, in the related art, special types of output modules have been prepared in response to the kind of power sources of the loads.
Thus manufacturers must make and prepare various kinds of output modules for different requests from users. This results in complexity in the production line, complexity in the process control and a problem that much storage space is required for the different types.
Further, OEM manufacturers must use output modules properly, and test and confirm many kinds of output modules. This also results in complexity of the product manufacturing, and in the possibility of component damage if the wrong one is used.
Further more end users must keep many kinds of output modules. This is also inconvenient.
Accordingly it is desirable to provide one kind of output module which is able to deal with various kinds of power sources.